This section is intended to provide a background or context to the disclosed embodiments. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.
Wireless communication systems are widely deployed to provide various types of communication content such as voice, data, and so on. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., bandwidth and transmit power). Examples of such multiple-access systems include code division-multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, 3GPP Long Term Evolution (LTE) systems, and orthogonal frequency division multiple access (OFDMA) systems.
Uplink transmitter power control in a mobile communication system balances the need for sufficient energy transmitted per bit to achieve a desired quality-of-service (e.g., data rate and error rate), against the need to minimize interference to other users of the system and to maximize the battery life of the mobile terminal. To accomplish this goal, uplink power control has to adapt to the characteristics of the radio propagation channel, including path loss, shadowing, fast fading and interference from other users in the same cell and adjacent cells.
In LTE Rel-8, power control of the physical uplink shared channel (PUSCH) is managed by a closed-loop accumulative power control (APC) algorithm that, in response to channel conditions, increments or decrements transmit power in discrete step sizes, whereupon the respective increments or decrements are disabled if the power reaches a configured maximum or minimum power level. The computation of the transmit power is based on the scheduled PUSCH transmission. However, depending on the scheduled PUSCH transmission, this algorithm can result in over-power or under-power conditions when the bandwidth and/or the modulation/coding scheme of the uplink channel is increased or decreased in response to changing resource grants.